/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.servlet.resource;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

/**
 * Abstract base class for {@link VersionStrategy} implementations.
 *
 * <p>Supports versions as:
 * <ul>
 * <li>prefix in the request path, like "version/static/myresource.js"
 * <li>file name suffix in the request path, like "static/myresource-version.js"
 * </ul>
 *
 * <p>Note: This base class does <i>not</i> provide support for generating the
 * version string.
 *
 * @author Brian Clozel
 * @author Rossen Stoyanchev
 * @since 4.1
 */
public abstract class AbstractVersionStrategy implements VersionStrategy {

    protected final Log logger = LogFactory.getLog(getClass());

    private final VersionPathStrategy pathStrategy;


    protected AbstractVersionStrategy(VersionPathStrategy pathStrategy) {
        Assert.notNull(pathStrategy, "VersionPathStrategy is required");
        this.pathStrategy = pathStrategy;
    }


    public VersionPathStrategy getVersionPathStrategy() {
        return this.pathStrategy;
    }


    @Override
    @Nullable
    public String extractVersion(String requestPath) {
        return this.pathStrategy.extractVersion(requestPath);
    }

    @Override
    public String removeVersion(String requestPath, String version) {
        return this.pathStrategy.removeVersion(requestPath, version);
    }

    @Override
    public String addVersion(String requestPath, String version) {
        return this.pathStrategy.addVersion(requestPath, version);
    }


    /**
     * A prefix-based {@code VersionPathStrategy},
     * e.g. {@code "{version}/path/foo.js"}.
     */
    protected static class PrefixVersionPathStrategy implements VersionPathStrategy {

        private final String prefix;

        public PrefixVersionPathStrategy(String version) {
            Assert.hasText(version, "Version must not be empty");
            this.prefix = version;
        }

        @Override
        @Nullable
        public String extractVersion(String requestPath) {
            return (requestPath.startsWith(this.prefix) ? this.prefix : null);
        }

        @Override
        public String removeVersion(String requestPath, String version) {
            return requestPath.substring(this.prefix.length());
        }

        @Override
        public String addVersion(String path, String version) {
            if (path.startsWith(".")) {
                return path;
            } else {
                return (this.prefix.endsWith("/") || path.startsWith("/") ?
                        this.prefix + path : this.prefix + '/' + path);
            }
        }
    }


    /**
     * File name-based {@code VersionPathStrategy},
     * e.g. {@code "path/foo-{version}.css"}.
     */
    protected static class FileNameVersionPathStrategy implements VersionPathStrategy {

        private static final Pattern pattern = Pattern.compile("-(\\S*)\\.");

        @Override
        @Nullable
        public String extractVersion(String requestPath) {
            Matcher matcher = pattern.matcher(requestPath);
            if (matcher.find()) {
                String match = matcher.group(1);
                return (match.contains("-") ? match.substring(match.lastIndexOf('-') + 1) : match);
            } else {
                return null;
            }
        }

        @Override
        public String removeVersion(String requestPath, String version) {
            return StringUtils.delete(requestPath, "-" + version);
        }

        @Override
        public String addVersion(String requestPath, String version) {
            String baseFilename = StringUtils.stripFilenameExtension(requestPath);
            String extension = StringUtils.getFilenameExtension(requestPath);
            return (baseFilename + '-' + version + '.' + extension);
        }
    }

}
